The need to increase the storage density and data transfer rate of information storage media (such as magnetic or optical storage) is a well known goal in the art. In a typical such device, the data is stored formatted as a track in which the data is encoded as orientation of the magnetization of the media as in magnetic recording or the presence or absence of an optical mark in the case of optical storage. The data is retrieved with a read transducer element that produces a signal that varies with the encoded data on the storage medium. This signal is processed by a device known as a read channel whose purpose is to recover the original data with high reliability taking account of the characteristics of the storage medium and the read transducer.
As the data is stored at a high density, the response of the transducer is usually spread across a number of encoded data symbols on the medium. Hence the received signal from the read transducer is a combination of the encoded data symbol below the transducer as well as encoded data symbols before and after that symbol. This characteristic of the system is known as inter-symbol interference (ISI). It is well known in the art how to implement efficient read channels to account for this and recover the data reliably in the presence of such inter-symbol interference.
As the read transducer responds to encoded data symbols in the near vicinity, the tracks of encoded data are normally separated by a distance sufficient to ensure that interference from adjacent tracks is small enough to limit its effect on the data recovery process.
In order to achieve higher density storage, the distance between the tracks can be reduced. Furthermore, to achieve higher data transfer rates, the use of a multiple head transducer which consists of a number of read transducers (NR) rigidly fixed together can be employed. In this case, a number of tracks can be written and/or read simultaneously thus resulting in an increase of data transfer rates by a factor NR.
The resulting read signals then consist of interference in both the track direction as well as interference between tracks. Hence, there is a need to develop a read channel system that can take these signals and efficiently recover the original data with high reliability taking account of this two dimensional ISI.